Why does the number of pixels per scan vary among different Level-2 AMSR-E data sets?
A typical AMSR-E swath width consists of approximately 2000 scans, with 243 pixels per scan for the 6.9 GHz to 36.5 GHz channels, and 486 pixels per scan for the 89.0 GHz channel.
In 2002, the AMSR-E science team discovered distortion along the outer 23 to 24 pixels of each swath. Some algorithm developers, including those for the Level-2A brightness temperature data set (AE_L2A) and the Level-2B rain data set (AE_Rain), decided it was important to still keep those outer pixels in the final products. Thus, AE_L2A has 243 pixels per scan (6.9 GHz to 36.5 GHz) or 486 pixels per scan (89 GHz). The Level-2B rain data set (AE_Rain) is derived from 89 GHz data, so it also has 486 pixels per scan.
The Level-2B ocean data set (AE_Ocean) algorithm developers, however, decided to trim the distorted pixels from their product, keeping only the center 196 pixels.
All algorithm developers for Level-2B and Level-3 data sets have been asked to reevaluate whether they still want to keep the outer pixels or not. Thus, the swath width may change among products in the future.